Single crystals of semi-organic non-linear optical (NLO) L-histidine tetrafluoroborate (L-HFB) have been successfully grown from three different pH (1.8, 3.2, and 4.2) solutions by evaporation and temperature lowering method. Solubility Of L-HFB crystals (grown from different solution pH) has been estimated. Crystals grown at lower pH values are observed to have higher solubility. The grown crystals have been subjected to powder X-ray diffraction studies to identify the crystalline nature. Single crystal X-ray diffractometer was utilized to measure unit cell parameter and morphology of grown crystal. The FTIR spectra taken for the crystals grown at different pH values show variations in the peak intensity. The NLO property is found to be varying with the change in pH values. The differential scanning calorimetry confirms the stability of the crystal up to 250degreesC. The microhardness studies reveal the changes in the mechanical property of the crystals grown from different pH values. (C) 2003 Published by Elsevier Science B.V.